Hi there, Nathan!
On your off day, you might consider spending a good part of the time at your Resort pool. Meals can be eaten (and, depending upon your Resort, ordered!) poolside. Additionally. Cast Members generally show up in the afternoon with fun pool games and activities for the children. There will be games both on land and in the water.
Or go big, and enjoy a day at one of the water parks!
Typhoon Lagoon is definitely a blast for all ages;
Blizzard Beach skews a bit older, but both of the parks offer a variety of smaller slides. family slides, and a kid-special splash area.
Touring the Resorts is always fun, too. Take the monorail ride around once, and then get off at each of the Resorts on the monorail line. You might pick a new place for lunch, or wander the grounds of the Resorts to determine where you'll next stay. Try the
BoardWalk area, too. While it really shines at night, there is always something to fin to explore during the day.
And then, of course, there's
Downtown Disney. If you can restrict your shopping to your day off, you can stroll the shops and choose souvenirs that you won't find anywhere else in the world. There's always some fun street entertainment, people-watching, and delicious snack and meal spots.
Have a wonderful trip!
See you later, celebrator,
-Deborah B.